The present invention relates in general to a motor assembly, and in particular to a force feedback motor assembly that provides an output in one or more degrees of freedom for use in joystick and other applications and more particularly to an improved force feedback joystick.
Various force feedback motor designs providing multiple degrees of freedom are known in the art for use in a wide variety of applications. For example, multiple degrees of freedom in motor output are particularly useful in linear actuation and positioning applications. Another application in which such motors may be used is in joystick applications for real control of an associated apparatus, e.g., direct control of an aircraft, wheelchair, or other vehicle, or for simulation apparatus control, e.g. video games, flight simulation, virtual reality simulation, etc. In these applications a control system may be provided for sensing a user""s manipulation of a joystick, i.e., the motor output shaft, and providing a signal for controlling the application.
Many applications also require force or tactile (xe2x80x9chapticxe2x80x9d) feedback to the user. The need for the user to obtain realistic tactile information and experience tactile sensation is extensive in many kinds of simulation and other applications. For example, in medical/surgical simulations, the xe2x80x9cfeelxe2x80x9d of a probe or scalpel simulator is important as the probe is moved within the simulated body. It would be invaluable to a medical trainee to learn how an instrument moves within a body, how much force is required depending on the operation performed, the space available in a body to manipulate an instrument, etc. In simulations of vehicles or equipment, force feedback for controls such as a joystick can be necessary to realistically teach a user the force required to move the joystick when steering in specific situations, such as in a high acceleration environment of an aircraft. Alternatively, when actually operating in a high acceleration vehicle environment, the force feedback can be used to counteract the effect of the acceleration induced forces on the hand and thus improve controllability and safety of the vehicle. In virtual world simulations where the user can manipulate objects, force feedback is necessary to realistically simulate physical objects; for example, if a user touches a pen to a table, the user should feel the impact of the pen on the table. An effective human/computer interface, such as a joystick, not only acts as an input device for tracking motion, but also as an output device for producing realistic tactile sensations. An interface that accurately responds to signals having fast changes and a broad range of frequencies as well as providing such signals accurately to a control system, is therefore desirable in these and other applications.
In addition, there is a desire to provide force feedback to users of computer systems in the entertainment industry. Joysticks and other interface devices can be used to provide force feedback to a user playing a video game or experiencing a simulation for entertainment purposes. Through such an interface device, a computer system can convey to the user the physical sensation of colliding into a wall, moving through a liquid, driving over a bumpy road, and other sensations. The user can thus experience an entire sensory dimension in the gaming experience that was previously absent. Force feedback interfaces can provide a whole new modality for human-computer interaction.
In typical multi-degree of freedom apparatuses that are capable of providing force feedback, there are several disadvantages. Generally conventional devices are cumbersome and complex mechanisms that are difficult and expensive to manufacture. In particular, the use of a transmission between the actuator motor and the joystick reduces the performance of the device and reduces the reliability and life of the device. Many transmission types can fail in a manner that renders the device unusable. For industrial and military applications, reliability and maintenance concerns are sometimes linked to the safety of personnel. If a force feedback device is not reliable or failsafe, then its use in these applications may be restricted or prevented even though the force feedback capability would enhance the performance and safety for that application.
In consumer markets, low-cost is highly desirable. For example, personal computers for the home consumer are becoming powerful and fast enough to provide force feedback to the typical mass-market consumer. A need is thus arising to be able to manufacture and market force feedback interfaces as cheaply and as efficiently as possible. The cost, complexity, reliability, and size of a force feedback interface for home use should be practical enough to mass-produce the devices. In addition, aesthetic concerns such as compactness and operating noise level of a force feedback device are of concern in the home market. Since the prior art feedback interfaces are mainly addressed to specific applications in industry, most force feedback mechanisms are costly, large, heavy, are easily broken, have significant power requirements, and are difficult to program for applications. The prior art devices require high-speed control signals from a controlling computer for stability, which usually requires more expensive and complex electronics. In addition, the prior art devices are typically large and noisy. These factors provide many obstacles to the would-be manufacturer of force-feedback interfaces to the home computer market.
Accordingly, there is a need in the art for a reliable motor allowing output in multiple degrees of freedom and capable of providing force feedback that may be efficiently and cost-effectively produced.
The present invention is organized about the concept of providing a reliable and cost-efficient force feedback motor allowing multiple degrees of output freedom. In particular, a force feedback motor consistent with the invention may include: a stator having an interior surface forming at least a portion of a sphere or curved surface and first and second substantially orthogonally positioned stator coils wound on the interior (or exterior) surface; and a rotor fixed to the output shaft and movably supported adjacent the stator with an air gap disposed between the rotor and the stator, the rotor including one or a plurality of magnetic field generators disposed thereon and being movable along the interior surface in directions defining at least first and second degrees of freedom. Upon energization of the first stator coil, a first magnetic field is established to force at least a first one of the magnets and the rotor in a direction in the first degree of freedom. Upon energization of the second stator coil, a second magnetic field is established to force at least a second one of the magnets and the rotor in a direction in the second degree of freedom. The first degree of freedom may be parallel to the second stator coil and the second degree of freedom may be parallel to the first stator coil.
The interior surface of the stator may be defined by a stator back iron comprising a ferromagnetic material. Each of the rotor magnets may also be arranged on a rotor back iron comprising a ferromagnetic material. The rotor magnets may be permanent magnets or electromagnets.
The rotor magnets may be arranged to form different sides of a parallelogram, with first and second ones of the magnets defining a first pair of parallel sides of the parallelogram parallel to the first stator coil, and third and fourth ones of the magnets defining a second pair of parallel sides of the parallelogram parallel to the second stator coil. The parallelogram defined by the magnets may be a square. Also, the first and third ones of the magnets advantageously may be configured with north poles disposed adjacent the stator coils, and the second and fourth ones of the magnets are configured with south poles disposed adjacent the stator coils.
The rotor may be supported adjacent the stator by a gimbal mechanism connected to the output shaft, e.g., a joystick handle, and supported on the stator. The gimbal mechanism may be configured to establish pivot points for the output shaft to allow motion of the rotor in the first and second degrees for freedom, the pivot points being substantially aligned with an equator of the sphere or curved surface.
According to the invention, there is also provided a method of providing force feedback to the joystick handle in response to manipulation of the handle by a user. The method includes: providing a motor consistent with the invention with the joystick being the output shaft; sensing a position of the joystick; energizing at least one of the coils based on the position to establish the feedback force against at least the first one of the magnets and the rotor.
It is an object of the present invention to provide a motor having an output shaft movable in multiple degrees of freedom. The motor comprising a stator and a rotor. The stator having an interior surface with first and second stator coils wound thereon, wherein the stator coils are positioned substantially orthogonally to each other. The rotor being fixed to the output shaft and movably supported adjacent the stator with an air gap disposed between the rotor and the stator, the rotor including at least one magnet disposed thereon and being movable along said interior surface in directions defining at least first and second degrees of freedom, wherein upon energization of the first stator coil, a first magnetic field is established to urge the rotor to rotate in a direction of the first degree of freedom, and upon energization of the second stator coil, a second magnetic field is established to urge the rotor to rotate in a direction of the second degree of freedom, the second degree of freedom substantially perpendicular to the first degree of freedom.
It is a further object of the invention to provide a motor having an output shaft movable in multiple degrees of freedom. The motor comprising a stator and a rotor. The stator having an interior surface and first and second stator coils wound in close proximity to the interior surface. The stator coils being positioned substantially orthogonally to each other. The stator comprising a plurality of laminations radially disposed about a center point with a plane of each lamination extending through the center point. The rotor being fixed to the output shaft and movably supported adjacent the stator with an air gap disposed between the rotor and the stator. The rotor including at least one magnet disposed thereon and being movable along the interior surface in directions defining at least first and second degrees of freedom.
It is a further object of the invention to provide a motor having an output shaft movable in multiple degrees of freedom. The motor comprising a stator and a rotor. The stator having an interior surface and first and second stator coils wound in close proximity to the interior surface. The stator coils positioned substantially orthogonally to each other. The stator comprising a first plurality and a second plurality of parallel laminations arranged in an arc about a center point, the first plurality arranged perpendicular to the second plurality. The rotor being fixed to the output shaft and movably supported adjacent the stator with an air gap disposed between the rotor and the stator. The rotor further comprising at least one magnet disposed thereon and being movable along the interior surface in directions defining at least first and second degrees of freedom.
It is a further object of the invention to provide a motor having an output shaft movable in multiple degrees of freedom. The motor comprising a stator and a rotor. The stator having an interior surface and first and second stator coils wound in close proximity to the interior surface. The stator coils positioned substantially orthogonally to each other. The stator comprising a first plurality and a second plurality laminations arranged in an arc about a center point, the first plurality arranged perpendicular to the second plurality. The rotor fixed to the output shaft. The rotor comprising a cross linkage having a first arm extending radially from the output shaft and a second arm extending radially from the output shaft with the first arm fixed to and orthogonal to the second arm. The rotor further comprising a first permanent magnet disposed at a distal end of the first arm and a second permanent magnet disposed at a distal end of the second arm. The first and the second magnets movably supported adjacent along the interior surface of the stator in directions defining at least first and second degrees of freedom.
It is a further object of the invention to provide a lamination for use in a stator. The lamination comprising a ferromagnetic material having an arcuate surface orthogonal to a side surface and a plurality of parallel slots.